Something extremely awesome! So awesome it's almost too awesome for anyone to handle.

Like a potato peeler made of the bones from your enemies! That's awesomesauce!

"I have a potato peeler made of the bones from my enemies!"
"Wow, that's totally awesomesauce man!"

- or -

"Did you hear Jan got demoted in CS:GO?"
"No I didn't! That's awesomesauce!"
"Yeah, almost as awesomesauce as when Oliver exercised!"
"He did?! He must've totally ruined the balance of the universe!"
"Yeah, he did"
*Both at the same time*
"Awesomesauce"